9-Fluorenyl radical: Electrochemical generation and cathodic immobilization at solid interfaces

Abstract

9-Bromofluorene (FluHBr) is electrochemically reduced at solid electrodes such as glassy carbon (GC) and smooth transition metal surfaces (gold, palladium, and platinum). At smooth palladium or gold, two well-separated steps are obtained and are assigned (i) to the electro-catalytic formation of the radical and then (ii) to its reduction. Additionally, galvanostatic depositions of different transition metals (Pd, Au, Ni, Co, and Rh) onto solid substrates like glassy carbon, platinum and gold lead to comparable results. It is worth noting that the potential of the second reduction step remains the same whatever the metal. Fixed potential electrolyses at the level of the first step permitted to obtain (especially at Au and GC surfaces) cathodic signals assigned to the grafting of 9-fluorenyl radical FluH ●. The transient formation of this radical has been established by means of electron spin resonance (electrolysis at low temperature or trapping by a nitrone).